An Integrated coal Gasification Combined Cycle (IGCC) is a power generation technology which uses a flammable gas, which is obtained by gasifying a hydrocarbon originating fuel such as coal, biomass, or petroleum residue oil, as the fuel.
The IGCC plant includes a gas turbine which uses the flammable gas as a fuel, and a steam turbine which is operated by steam obtained by recovering exhaust heat of the gas turbine. The IGCC plant further includes a generator which is configured so as to be coaxial with the gas turbine and the steam turbine or a generator which is multiaxially configured, and drives the generator by the gas turbine and the steam turbine so as to generate power.
Hereinafter, a configuration of the IGCC will be described with reference to FIG. 1. FIG. 1 is an example of a configuration diagram of the IGCC. Coal supply equipment 1 crushes raw coal and supplies pulverized coal to a gasifier 2. An air separation device 10 sucks air from atmosphere, separates the air into nitrogen and oxygen, and supplies the separated nitrogen and oxygen to the gasifier 2. In addition, an air booster 11 sucks air and supplies compressed air to the gasifier 2. The nitrogen supplied from the air separation device 10 is used so as to transport coal and char. In addition, the oxygen supplied from the air separation device 10 and the compressed air supplied from the air booster 11 are used so as to gasify coal. The gasifier 2 burns the coal and generates fuel gas. The fuel gas is fed to a high temperature filter 3. The high temperature filter 3 recovers the char. The fuel gas is also fed to gas purification unit 4, and sulfur compounds, nitrogen compounds, or the like are removed. The refined fuel gas is supplied to a combustor 5 of the gas turbine while a flow rate of the fuel gas is controlled by a gas turbine governor 14. The gas turbine burns fuel gas with air sucked from a gas turbine compressor 7, and the gas turbine 6 operates. A HRSG 12 recovers exhaust heat of the gas turbine in order to generate steam, and supplies the steam to a steam turbine 8. The steam turbine 8 is operated by the supplied steam. Flue gas produced when the steam is generated is discarded from a stack 13. Shafts of the gas turbine 6 and the steam turbine 8 are connected to a generator 9, and the gas turbine 6 and the steam turbine 8 drive the generator 9 so as to generate power.
A control device 50 controls an output of the Integrated coal Gasification Combined Cycle. Hereinafter, an output control of the related art will be described with reference to FIG. 6. FIG. 6 is a diagram showing an example of an output control system of the IGCC in the related art. The control device 50 determines a generator output command (MWD) according to a demand load (S100). Next, the control device 50 calculates a deviation between an output value (S101) of the generator 9 measured by a predetermined method and the generator output command (S102). The control device 50 performs a GT control (S103) which corrects the deviation, and adjusts an opening degree of the gas turbine governor (“GT GOV”) 14 (S104).
Moreover, the control device 50 calculates a base gasifier input command (GIDO) (S108) and a set value of a system gas pressure based on the generator output command in parallel with the processing (S100 to S104). In order to calculate the set value of the system gas pressure from the generator output command, a function FX is used (S109).
In addition, the control device 50 acquires an actual measurement value (S110) of the system gas pressure which is measured by a pressure gauge 15, and calculates a deviation between the actual measurement value and the set value of the system gas pressure (S111). The control device 50 calculates gasifier input command corrections which indicate flow rates of coal, air, and oxygen input to the gasifier 2 based on the calculated pressure deviation (S112). The control device 50 adds the base gasifier input command to the gasifier input command corrections (S113), and obtains a gasifier input command (GID) (S114). The control device 50 calculates a coal flow rate command (S115), an air flow rate command (S116), and an oxygen flow rate command (S117) from the gasifier input command, and controls the coal, the oxygen, and the air input to the gasifier 2. In this way, the control device 50 performs a feedback control such as a Proportional Integral (PI) control using the gasifier input command correction which corrects the pressure deviation calculated in S111.
In this output control, in a case where a load is constant and a power generation amount is set, the value of the gasifier input command correction is approximately zero except that the gasifier input command correction is changed so as to compensate for external disturbances such as in atmospheric temperature. Meanwhile, when the load is changed, the control device 50 adjusts an opening degree of the gas turbine governor 14 so as to correspond to temporal changes in the generator output command, and controls the output of the generator 9. In this case, the gasifier input command correction is a value which suppresses a pressure change generated by the change of the output. At this time, the gasifier input command (GID) is a sum of the base gasifier input command (GIDO) determined by the generator output command and the gasifier input command correction which compensates for the pressure deviation caused by the load change.
In addition, Japanese Patent No. 4745940 discloses a technology which performs an output control by adding, to the gasifier input command, a gasifier input acceleration command “GIR” which is a value for promoting an operation state of a gasifier 2 in which a load can be smoothly changed.